Composition and Method for Reducing Friction in Internal Combustion Engines

ABSTRACT

A fuel composition comprising a combustible fuel, an effective friction reducing amount of at least one saturated C 5  to C 31  α-glycerol ether, and a detergent package is disclosed, as well as a method of reducing the amount of friction in an internal combustion engine by adding the fuel composition to the engine.

This application claims the benefit of U.S. Provisional Application No. 61/288,471 filed Dec. 21, 2009, the entirety of which is expressly incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates generally to friction modifiers and, more particularly, to a new fuel composition and method for reducing friction in internal combustion engines.

BACKGROUND OF THE INVENTION

Much of the focus over the past twenty years has been devoted to fuel additives which control deposit formation in the fuel induction systems of spark ignition internal combustion engines. These deposit control additives have been formulated to effectively control carbonaceous deposits on the fuel injectors, the intake valves and the combustion chamber in an effort to maintain or achieve engine cleanliness.

As crude consumption and fuel costs steadily increased over the past decade, consumers have expressed a growing interest and have placed a greater emphasis on the importance of improvements in vehicle fuel economy. In particular, there has been a strong consumer interest for additives which can offer reduced engine wear, lower emissions, and improved fuel economy. Unfortunately, the deposit control additives provide very little friction reduction performance at typical concentrations used in commercial fuels. Therefore, no additional fuel economy benefit would be expected over and above that achieved through deposit control within the engine.

During this same time period, there have been many advances in engine design directed toward better fuel economy and more power generation (specifically more horsepower and acceleration). Conventional port-fuel injection (PFI) is the primary fuel delivery technology used in gasoline engines. PFI engines inject gasoline into the intake port along with the intake air to form a homogeneous mixture for combustion. This is done in an attempt to optimize the combustion of the fuel and provide improved engine performance. In addition, many other engine management control technologies have been developed to further optimize the combustion process for improved fuel economy in PFI engines.

More recently, gasoline direct injection (GDI) engines have been developed to provide improved fuel economy while maintaining or generating more engine-out power. The GDI engine injects gasoline directly into the combustion chamber separate from the air intake which allows the engine management system to better optimize the combustion process according to the load conditions. Both PFI and GDI engines require fuel additives to control deposits in the injectors, intake valves and combustion chamber. In addition, further fuel economy improvement could be achieved by reducing the friction between the cylinder liner and piston ring interface, the valve train and the fuel pump, especially in GDI engines. Therefore, there is a need in the petroleum industry to develop a fuel and fuel additive package that addresses the engine deposit and friction reduction requirements of PFI and GDI engines.

Due to the fact that lubricants have traditionally been used to minimize engine friction, and an estimated 25 to 50% of the frictional losses of an engine occur at the cylinder liner and piston ring interface, the lubricant industry was the first to focus on reducing engine friction and improving fuel economy. Improvements in fuel economy have been achieved through the lowering of the motor oil viscosity. However, at conditions where the engine is working hard (high load and high temperature), such as hard acceleration or going up hill, lower viscosity oils can produce very thin lubricant films which may increase the potential for metal-to-metal contact and lead to wear and higher friction, i.e., lower fuel economy. To help reduce this contact and improve engine lubrication under these boundary layer conditions, both inorganic and organic friction modifiers have been utilized, but GF-4 motor oil requirements have reduced the level of inorganic friction modifiers allowed due to phosphorus deactivation of the catalytic converter. This has forced the lubricant industry to rely more heavily on organic friction modifiers.

Organic friction modifiers are compounds that can affect the boundary layer conditions experienced by the cylinder liner and piston ring interface under these severe engine operating conditions. These types of friction modifiers are surface active and produce a protective coating on the metal surface of the engine by forming a monolayer through the interaction of the metal surface with the polar end of the friction modifier. Subsequent layers of the friction modifier can then build up to provide friction reduction in the boundary layer and help to prevent the two surfaces and their asperities from contacting each other. The challenge in overcoming the frictional design limitations, however, lies in identifying a friction modifier which can influence the boundary layer properties without leading to undesirable effects, such as intake valve deposits and oil thickening.

The application of organic friction modifiers in combustible fuels has been pursued for some time with minimal success. Friction modifier additives and detergents commonly added to combustible fuels are generally higher molecular weight compounds that may not be completely burned during the combustion process within spark ignition engines. As a result, some of the additive interacts with the lubricant oil film present in the combustion cylinder. This interaction allows some of the additive to become mixed with the lubricant. As the lubricant oil film is replenished, it becomes mixed with fresh lubricant from the main lubricant reservoir and some of the absorbed additive migrates past the piston rings and into the oil pan. As a result, there is a slow transfer of additive from the fuel to the lubricant. Depending on the driving cycle, the amount of additive that is transferred from the fuel to the lubricant can be as high as about 30%. Based on typical friction modifier additive concentrations expected for gasoline, this level of transfer may lead to friction modifier concentrations in the lubricant of up to about 0.5 wt % over a 5,000 mile lube drain interval. Therefore, the addition of an organic friction modifier to a combustible fuel can impact the cylinder liner and piston ring frictional interaction directly within the combustion chamber and can also accumulate in a lubricant to improve the frictional properties in other parts of the engine drive train contacted by the motor oil (e.g., valve train, cam shaft, bearings, etc.). This transfer of the friction modifier is known in the art and taught, for example, in WO 01/72390 A2, which describes the delivery mechanism by which a fuel born friction modifier can be transferred to the cylinder liner/piston ring interface and can accumulate in the lubricating oil sump, thus resulting in improved lubrication throughout the engine.

Accordingly, it would be desirable to provide a new fuel composition which contains a combustible fuel, a detergent package and a friction modifier that has a strong affinity for metal surfaces, but not so strong as to leave deposits. It would also be desirable to provide a method for reducing the amount of friction in an internal combustion engine by adding the new fuel composition to the engine to positively impact the friction of the cylinder liner and piston ring interface and the drive train of the engine, and lead to reduced wear, lower emissions, higher fuel economy and increased net horsepower.

SUMMARY OF THE INVENTION

In accordance with the present invention, the fuel composition comprises a combustible fuel, an effective friction reducing amount of at least one saturated C₅ to C₃₁ α-glycerol ether, and a detergent package.

In another aspect, the invention provides a fuel additive composition comprising an effective friction reducing amount of at least one saturated C₅ to C₃₁ α-glycerol ether and a detergent package.

The invention also provides a method of reducing the amount of friction in an internal combustion engine comprising the step of adding to the engine a fuel composition comprising a combustible fuel, an effective friction reducing amount of at least one saturated C₅ to C₃₁ α-glycerol ether, and a detergent package.

The inventive method effectively reduces the amount of friction in an internal combustion engine by adding the fuel composition of the present invention to the engine, thus leading to reduced wear, lower emissions, higher fuel economy, and increased net horsepower.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a new fuel composition and method for reducing the amount of friction in an internal combustion engine. In accordance with the invention, the fuel composition comprises a combustible fuel, an effective friction reducing amount of at least one saturated C₅ to C₃₁ α-glycerol ether, and a detergent package. The fuel composition is added to the internal combustion engine to effectively reduce the amount of friction in the engine.

In accordance with the invention, the combustible fuels which may be used include gasoline and diesel fuel, with the preferred fuel being gasoline. Gasoline comprises blends of C₄-C₁₂ hydrocarbons which boil in the range of 25° C. to 225° C., and satisfy international gasoline specifications, such as ASTM D-4814 and EN228. These gasoline blends typically contain mixtures of normal and branched paraffins, olefins, aromatics and naphthenic hydrocarbons, and other liquid hydrocarbon containing components suitable for spark ignition gasoline engines, such as conventional alcohols and ethers.

The gasoline can be derived from petroleum crude oil by conventional refining and blending processes, such as straight run distillation, hydrocracking, fluid catalytic cracking, thermal cracking, and various reforming technologies.

The saturated C₅ to C₃₁ α-glycerol ethers which may be used as friction modifiers in the practice of the invention include hexyl-, octyl-, decyl-, dodecyl-, tetradecyl-, hexadecyl-, octadecyl-, eicosyl-, docosyl-, tetracosyl-glycerol ethers, and mixtures thereof. Preferable saturated C₅ to C₃₁ α-glycerol ethers include, but are not limited to, saturated C₁₅ to C₂₅ α-glycerol ethers. A hexadecyl-glycerol ether (also known as chimyl alcohol) is a preferred saturated C₁₅ to C₂₅ α-glycerol ether, with an octadecyl-glycerol ether (also known as batyl alcohol) being the most preferred. Examples of suitable octadecyl-glycerol ethers include Batyl Alcohol EX available from Nikko Chemicals Co., Ltd., and Batyl Alcohol available from TCI America Laboratory Chemicals.

The fuel composition preferably contains an effective friction reducing amount of the saturated C₅ to C₃₁ α-glycerol ether in the range of from about 1 ppm to about 2000 ppm (parts per million). More preferably, the amount of the saturated C₅ to C₃₁ α-glycerol ether present in the fuel composition is in the range of from about 5 ppm to about 1000 ppm, with about 10 ppm to about 500 ppm being most preferred.

The detergent packages which may be used in the practice of the present invention are well known to those skilled in the art and commercially available. Suitable commercial detergent packages include, but are not limited to, Keropur® and Kerocom® packages available from BASF A.G., HiTEC® packages available from Afton Chemical Corporation, and OGA® packages available from Chevron Oronite Company LLC.

The detergent packages typically include at least one deposit control additive, a corrosion inhibitor, a carrier fluid, and a solvent. Some commercially available detergent packages do not contain a corrosion inhibitor and may be used in the practice of the present invention, however, it is preferred that a corrosion inhibitor be included. The appropriate amount of each component in the detergent package will vary depending upon the specific engine performance benefit being sought and can be readily determined by those skilled in the art.

The detergent package typically contains at least one high molecular weight nitrogen-containing deposit control additive. Examples of such deposit control additives include polyalkylene amines, polyalkylene succinimides, Mannich bases, and polyether amines. The preferred deposit control additive for use in the present invention is a polyisobutylene (PIB) amine. Examples of suitable PIB-amines are taught in U.S. Pat. No. 4,832,702, the disclosure of which is incorporated herein by reference.

The corrosion inhibitors which may be utilized in the practice of the present invention include, but are not limited to, monomers, dimers, and trimers of long chain organic acids, and various esters, imides, thiadiazoles, and triazoles.

The carrier fluids which may be used in the detergent package are preferably compatible with the combustible fuel and have the ability to dissolve or disperse the components of the detergent package. Examples of conventional carrier fluids include mineral oils and synthetic oils, such as poly a-olefin oligomers, polyethers, polyether amines, and carboxylic esters of long chain alkanols.

There are various alcohols and aromatic hydrocarbons which may be used as solvents in the practice of the present invention. Examples of suitable solvents include xylenes, toluene, tetrahydrofuran, isopropanol isobutylcarbinol, and n-butanol; and petroleum hydrocarbon solvents, such as naphtha and the like.

The fuel composition may be added to an internal combustion engine by any conventional method and can be used in internal combustion engines that burn liquid fuel, especially spark-ignited gasoline engines encompassing carbureted, PFI and GDI, as well as in vehicles containing compression-ignited engines, such as diesel engines. When combustion of the fuel composition is achieved in the internal combustion engine, the amount of friction in the engine is effectively reduced, thus leading to reduced wear, lower emissions, higher fuel economy, and increased net horsepower.

In another aspect of the present invention, a fuel additive composition containing an effective friction reducing amount of at least one saturated C₅ to C₃₁ α-glycerol ether and a detergent package is provided. All of the suitable components which may be used in the fuel additive composition and their respective amounts are the same as those described above with respect to the fuel composition. The fuel additive may be combined with a combustible fuel in any conventional manner generally known to those having ordinary skill in the art to which this invention pertains and then added to an internal combustion engine to effectively reduce the amount of friction in the engine.

EXAMPLES

The following examples are intended to be illustrative of the present invention and to teach one of ordinary skill how to make and use the invention. These examples are not intended to limit the invention or its protection in any way.

Example 1

An SRV® instrument was utilized to determine the performance of a number of friction modifier additives. The SRV instrument measures the coefficient of friction and wear scar of a lubricant resulting from the oscillation of a ball on a disc at a constant set of conditions. SRV reciprocation tests were done using a commercial Castrol GTX® 5W30 (GF-4) motor oil that was spiked with various commercially available organic friction modifier additives.

The organic friction modifier additives tested were glycerol monooleate (GMO), which was obtained from Oronite Chemical Company, oleylamide (Crodamide® O), obtained from Croda Chemicals, glycerol monooleyl ether (FM-618C), obtained from Adeka USA, hexadecyl-glycerol ether (chimyl alcohol), obtained from Wako Chemicals USA, and octadecyl-glycerol ether (batyl alcohol), obtained from TCI America Laboratory Chemicals. Test samples were prepared by mixing each organic friction modifier with the Castrol GTX 5W30 motor oil in accordance with the treat rates set forth below in Table 1.

The SRV instrument uses a steel ball as the upper test piece and a steel disk as the lower test piece. An oil sample was placed on the disk, a load was applied to the ball from the top, and the ball was vibrated parallel to the disk as the ball was pressed against the disk. The lateral load applied to the disk was measured to calculate the coefficient of friction. The coefficient of friction was taken as the average of the data for a particular temperature. The SRV test conditions were 50 N load, 50 Hz oscillation, 1 mm stroke and 1 hour duration. The initial temperature was set to 80° C. for the first 30 minutes of testing and then rapidly raised to 120° C. for the final 30 minutes. This procedure provided some indication of the temperature dependence of the additive's effect on friction reduction at temperatures expected to be encountered between the cylinder liner and piston ring. The results of the testing are shown below in Table 1.

TABLE 1 Comparison of SRV Results Coefficient of Friction Treat Coefficient of Friction Modifier Rate Friction % Reduction Wear Scar Additive (wt %) 80° C. 120° C. 80° C. 120° C. mm Reduction (%) None N/A 0.143 0.145 N/A N/A 0.40 N/A GMO 0.5 0.137 0.137 4.2 5.5 0.31 22 FM-618C 0.5 0.131 0.130 8.4 10.3 0.33 17 Crodamide O 0.5 0.128 0.126 10.5 13.1 0.33 17 Chimyl Alcohol 0.5 0.124 0.119 13.3 17.9 0.30 25 Batyl Alcohol  0.05 0.137 0.134 4.2 7.6 0.35 12 Batyl Alcohol 0.1 0.131 0.127 8.4 12.4 0.31 22 Batyl Alcohol 0.2 0.124 0.123 13.3 15.2 0.33 17 Batyl Alcohol 0.5 0.115 0.108 19.6 25.5 0.28 30

The data in Table 1 illustrate the superior performance of the batyl alcohol (octadecyl-glycerol ether) relative to other known friction modifier additives. These data show that the coefficient of friction can be lowered by about 20% at 80° C. and 25% at 120° C. relative to that of a commercial Castrol GTX motor oil meeting the GF-4 specifications through the use of the batyl alcohol additive at the 0.5 wt % treat rate. Also, at the 0.5 wt % treat rate, the coefficient of friction values are significantly lower than those of the GMO and Crodamide O additives at both temperatures. Both the GMO and Crodamide O additives are well-known friction modifier chemistries and have been used extensively in motor vehicle lubricants. The superior performance is particularly demonstrated by the fact that the batyl alcohol surpasses the friction reduction performance of Crodamide O at a 60% lower treat rate (0.2 wt % versus 0.5 wt %). This is an important performance attribute since the friction modifier in the fuel will slowly accumulate in the lubricating oil, and therefore, the batyl alcohol will provide friction reduction at much lower concentration. In addition, the batyl alcohol may also act as a wear reducing additive since the wear scar was reduced by approximately 30% with the addition of batyl alcohol (0.5 wt % treat rate) relative to the non-additized Castrol GTX motor oil. This is a significant reduction when compared to the wear scars of the comparative friction modifiers shown in Table 1.

Although the effect of the batyl alcohol friction modifier was measured in motor oil, one skilled in the art would understand that the addition of a friction modifier to a combustible fuel results in the accumulation of the friction modifier in the motor oil over the typical drain interval of the vehicle. Therefore, testing of the friction modifier in the motor oil is a reliable alternative to more expensive and complex engine tests.

Therefore, the inventive composition and method can effectively reduce the amount of friction within an internal combustion engine (in particular, the cylinder liner and piston ring interface and the drive train) by producing improved lubricity. The lower friction in turn can lead to reduced wear, lower emissions, higher fuel economy, and an increase in net horsepower.

Example 2

Intake valve deposit measurements were carried out on a Ford 2.3L engine dynamometer Intake Valve Deposit (IVD) Keep Clean test stand according to a modified version of the standard ASTM D6201 procedure. Each fuel test utilized clean valves and a cleaned engine to determine the Keep Clean performance of the fuel and additive combinations. Three fuels were then evaluated for their Keep Clean performance over a 50 hour test following a Coordinating Research Council (CRC) drive cycle. The first was a gasoline meeting ASTM D4814 that contained no additives (base fuel). The second was the same base fuel with a minimum amount of a commercial detergent package (160 ppmv) as required by the US EPA (i.e., the lowest additive concentration or LAC) which contained a PIB-amine, corrosion inhibitor, carrier fluid, solvent and dye. The final test was the base fuel with 160 ppmv of batyl alcohol and no detergent package. At the end of each Keep Clean test, the engine was disassembled and the intake valve deposits and the total combustion chamber deposits (TCD) were quantitatively measured. The results are shown below in Table 2.

TABLE 2 Comparison of IVD Keep Clean Results Friction Modifier Treat Rate Average IVD, Average TCD, Additive (ppmv) mg mg None* N/A 375 N/A None** N/A 184 1166 Batyl Alcohol 160 312 1122 *Base fuel only, no detergent package. **Base fuel with detergent package.

The results illustrated in Table 2 demonstrate that although the batyl alcohol has a high metal/surface affinity as demonstrated by the SRV tests in Example 1, this affinity does not result in an increase in IVD as measured by the Keep Clean test. The base fuel with no detergent package results in about 375 mg of deposit per intake valve during the 50 hour test. In comparison, the same fuel with the batyl alcohol results in about 312 mg of deposit per intake valve. This indicates that the batyl alcohol is neutral to a slight improvement in Keep Clean. Additionally, the batyl alcohol does not lead to an increase in TCD when compared to the results of the base fuel with the detergent package (average of 1122 mg versus an average of 1166 mg). This data indicates that the batyl alcohol would be expected to be a desirable friction modifier since it has a strong affinity for metal surfaces, but does not leave deposits.

While the present invention is described above in connection with preferred or illustrative embodiments, these embodiments are not intended to be exhaustive or limiting of the invention. Rather, the invention is intended to cover all alternatives, modifications and equivalents included within its spirit and scope, as defined by the appended claims. 

1. A fuel composition comprising: a. a combustible fuel; b. an effective friction reducing amount of at least one saturated C₅ to C₃₁ α-glycerol ether; and c. a detergent package.
 2. The composition of claim 1 wherein the combustible fuel is selected from the group consisting of gasoline and diesel fuel.
 3. The composition of claim 1 wherein the saturated C₅ to C₃₁ α-glycerol ether is selected from the group consisting of hexyl-, octyl-, decyl-, dodecyl-, tetradecyl-, hexadecyl-, octadecyl-, eicosyl-, docosyl-, tetracosyl-glycerol ethers, and mixtures thereof.
 4. The composition of claim 3 wherein the saturated C₅ to C₃₁ α-glycerol ether is a saturated C₁₅ to C₂₅ α-glycerol ether.
 5. The composition of claim 4 wherein the saturated C₁₅ to C₂₅ α-glycerol ether is an octadecyl-glycerol ether.
 6. The composition of claim 1 wherein the amount of the saturated C₅ to C₃₁ α-glycerol ether is in the range of from about 1 ppm to about 2000 ppm.
 7. The composition of claim 1 wherein the amount of the saturated C₅ to C₃₁ α-glycerol ether is in the range of from about 5 ppm to about 1000 ppm.
 8. The composition of claim 1 wherein the amount of the saturated C₅ to C₃₁ α-glycerol ether is in the range of from about 10 ppm to about 500 ppm.
 9. The composition of claim 1 wherein the detergent package comprises: a. at least one deposit control additive; b. a corrosion inhibitor; c. a carrier fluid; and d. a solvent.
 10. A fuel additive composition comprising: a. an effective friction reducing amount of at least one saturated C₅ to C₃₁ α-glycerol ether, and b. a detergent package.
 11. The composition of claim 10 wherein the saturated C₅ to C₃₁ α-glycerol ether is selected from the group consisting of hexyl-, octyl-, decyl-, dodecyl-, tetradecyl-, hexadecyl-, octadecyl-, eicosyl-, docosyl-, tetracosyl-glycerol ethers, and mixtures thereof.
 12. The composition of claim 11 wherein the saturated C₅ to C₃₁ α-glycerol ether is an octadecyl-glycerol ether.
 13. The composition of claim 10 wherein the amount of the saturated C₅ to C₃₁ α-glycerol ether is in the range of from about 1 ppm to about 2000 ppm.
 14. The composition of claim 10 wherein the detergent package comprises: a. at least one deposit control additive; b. a corrosion inhibitor; c. a carrier fluid; and d. a solvent.
 15. A method of reducing the amount of friction in an internal combustion engine comprising the step of adding to the engine a fuel composition comprising a combustible fuel, an effective friction reducing amount of at least one saturated C₅ to C₃₁ α-glycerol ether, and a detergent package.
 16. The method of claim 15 wherein the combustible fuel is selected from the group consisting of gasoline and diesel fuel.
 17. The method of claim 15 wherein the saturated C₅ to C₃₁ α-glycerol ether is selected from the group consisting of hexyl-, octyl-, decyl-, dodecyl-, tetradecyl-, hexadecyl-, octadecyl-, eicosyl-, docosyl-, tetracosyl-glycerol ethers, and mixtures thereof.
 18. The method of claim 17 wherein the saturated C₅ to C₃₁ α-glycerol ether is an octadecyl-glycerol ether.
 19. The method of claim 15 wherein the amount of the saturated C₅ to C₃₁ α-glycerol ether is in the range of from about 1 ppm to about 2000 ppm.
 20. The method of claim 15 wherein the detergent package comprises: a. at least one deposit control additive; b. a corrosion inhibitor; c. a carrier fluid; and d. a solvent. 